Chapter I: The Detached Lever Escapement (2)

We next set the dividers so they embrace the space on the radial line _A b_ between its intersection with the line _B j_ and the center _A_, and from _A_ as a center sweep the arc _i_, said arc defining the _addendum_ of the escape-wheel teeth. We draw a line from the intersection of the radial line _A f_ with the arc _i_ to the intersection of the radial line _A g_ with the arc _a_, and thus define the impulse face of the escape-wheel tooth _D_. For defining the locking face of the tooth we draw a line at an angle of twenty-four degrees to the line _A g_, as previously described. The back of the tooth is defined with a curve swept from some point on the addendum circle _i_, such as our judgment will dictate.

In the drawing shown at Fig. 20 the radius of this curve was obtained by taking eleven and a half degrees from the degree arc of 5" radius in the dividers, and setting one leg at the intersection of the radial line _A f_ with the arc _i_, and placing the other on the line _i_, and allowing the point so established to serve as a center, the arc was swept for the back of the tooth, the small circle at _n_ denoting one of the centers just described. The length for the face of the tooth was obtained by taking eleven degrees from the degree arc just referred to and laying that space off on the line _p_, which defined the face of the tooth. The line _B k_ is laid off one and a half degrees below _B h_ on the arc _m_. The extent of this arc on the arc _d_ defines the locking face of the entrance pallet. We set off four degrees on the arc _m_ below the line _B k_, and through the point so established draw the line _B l_. We draw a line from the intersection of the line _A g_ with the line _c h_ to the intersection of the arc _e_ with the line _c l_, and define the impulse face of the entrance pallet.

RELATIONS OF THE SEVERAL PARTS.

Before we proceed to delineate the exit pallet of our escapement, let us reason on the relations of the several parts.

The club-tooth lever escapement is really the most complicated escapement made. We mean by this that there are more factors involved in the problem of designing it correctly than in any other known escapement. Most--we had better say all, for there are no exceptions which occur to us--writers on the lever escapement lay down certain empirical rules for delineating the several parts, without giving reasons for this or that course. For illustration, it is an established practice among escapement makers to employ tangential lockings, as we explained and illustrated in Fig. 16.

Now, when we adopt circular pallets and carry the locking face of the entrance pallet around to the left two and a half degrees, the true center for the pallet staff, if we employ tangent lockings, would be located on a line drawn tangent to the circle _a a_ from its intersection with the radial line _A k_, Fig. 21. Such a tangent is depicted at the line _s l'_. If we reason on the situation, we will see that the line _A k_ is not at right angles to the line _s l_; and, consequently, the locking face of the entrance pallet _E_ has not really the twelve-degree lock we are taught to believe it has.

We will not discuss these minor points further at present, but leave them for subsequent consideration. We will say, however, that we could locate the center of the pallet action at the small circle _B'_ above the center _B_, which we have selected as our fork-and-pallet action, and secure a perfectly sound escapement, with several claimed advantages.

Let us now take up the delineation of the exit pallet. It is very easy to locate the outer angle of this pallet, as this must be situated at the intersection of the addendum circle _i_ and the arc _g_, and located at _o_. It is also self-evident that the inner or locking angle must be situated at some point on the arc _h_. To determine this location we draw the line _B c_ from _B_ (the pallet center) through the intersection of the arc _h_ with the pitch circle _a_.

Again, it follows as a self-evident fact, if the pallet we are dealing with was locked, that is, engaged with the tooth _D''_, the inner angle _n_ of the exit pallet would be one and a half degrees inside the pitch circle _a_. With the dividers set at 5", we sweep the short arc _b b_, and from the intersection of this arc with the line _B c_ we lay off ten degrees, and through the point so established, from _B_, we draw the line _B d_. Below the point of intersection of the line _B d_ with the short arc _b b_ we lay off one and a half degrees, and through the point thus established we draw the line _B e_.

LOCATING THE INNER ANGLE OF THE EXIT PALLET.

The intersection of the line _B e_ with the arc _h_, which we will term the point _n_, represents the location of the inner angle of the exit pallet. We have already explained how we located the position of the outer angle at _o_. We draw the line _n o_ and define the impulse face of the exit pallet. If we mentally analyze the problem in hand, we will see that as the exit pallet vibrates through its ten degrees of arc the line _B d_ and _B c_ change places, and the tooth _D''_ locks one and a half degrees. To delineate the locking face of the exit pallet, we erect a perpendicular to the line _B e_ from the point _n_, as shown by the line _n p_.

From _n_ as a center we sweep the short arc _t t_, and from its intersection with the line _n p_ we lay off twelve degrees, and through the point so established we draw the line _n u_, which defines the locking face of the exit pallet. We draw the line _o o'_ parallel with _n u_ and define the outer face of said pallet. In Fig. 21 we have not made any attempt to show the full outline of the pallets, as they are delineated in precisely the same manner as those previously shown.

We shall next describe the delineation of a club-tooth escapement with pallets having equidistant locking faces; and in Fig. 22 we shall show pallets with much wider arms, because, in this instance, we shall derive more of the impulse from the pallets than from the teeth. We do this to show the horological student the facility with which the club-tooth lever escapement can be manipulated. We wish also to impress on his mind the facts that the employment of thick pallet arms and thin pallet arms depends on the teeth of the escape wheel for its efficiency, and that he must have knowledge enough of the principles of action to tell at a glance on what lines the escapement was constructed.

Suppose, for illustration, we get hold of a watch which has thin pallet arms, or stones, if they are exposed pallets, and the escape was designed for pallets with thick arms. There is no sort of tinkering we can do to give such a watch a good motion, except to change either the escape wheel or the pallets. If we know enough of the lever escapement to set about it with skill and judgment, the matter is soon put to rights; but otherwise we can look and squint, open and close the bankings, and tinker about till doomsday, and the watch be none the better.

CLUB-TOOTH LEVER WITH EQUIDISTANT LOCKING FACES.

In drawing a club-tooth lever escapement with equidistant locking, we commence, as on former occasions, by producing the vertical line _A k_, Fig. 22, and establishing the center of the escape wheel at _A_, and with the dividers set at 5" sweep the pitch circle _a_. On each side of the intersection of the vertical line _A k_ with the arc _a_ we set off thirty degrees on said arc, and through the points so established draw the radial lines _A b_ and _A c_.

From the intersection of the radial line _A b_ with the arc _a_ lay off three and a half degrees to the left of said intersection on the arc _a_, and through the point so established draw the radial line _A e_. From the intersection of the radial line _A b_ with the arc _a_ erect the perpendicular line _f_, and at the crossing or intersection of said line with the vertical line _A k_ establish the center of the pallet staff, as indicated by the small circle _B_. From _B_ as a center sweep the short arc _l_ with a 5" radius; and from the intersection of the radial line _A b_ with the arc _a_ continue the line _f_ until it crosses the short arc _l_, as shown at _f'_. Lay off one and a half degrees on the arc _l_ below its intersection with the line _f'_, and from _B_ as a center draw the line _B_ _i_ through said intersection. From _B_ as a center, through the intersection of the radial line _A b_ and the arc _a_, sweep the arc _g_.

The space between the lines _B f'_ and _B i_ on the arc _g_ defines the extent of the locking face of the entrance pallet _C_. The intersection of the line _B f'_ with the arc _g_ we denominate the point _o_, and from this point as a center sweep the short arc _p_ with a 5" radius; and on this arc, from its intersection with the radial line _A b_, lay off twelve degrees, and through the point so established, from _o_ as a center, draw the radial line _o m_, said line defining the locking face of the entrance pallet _C_.

It will be seen that this gives a positive "draw" of twelve degrees to the entrance pallet; that is, counting to the line _B f'_. In this escapement as delineated there is perfect tangential locking. If the locking face of the entrance-pallet stone at _C_ was made to conform to the radial line _A b_, the lock of the tooth _D_ at _o_ would be "dead"; that is, absolutely neutral. The tooth _D_ would press the pallet _C_ in the direction of the arrow _x_, toward the center of the pallet staff _B_, with no tendency on the part of the pallet to turn on its axis _B_. Theoretically, the pallet with the locking face cut to coincide with the line _A b_ would resist movement on the center _B_ in either direction indicated by the double-headed arrow _y_.

A pallet at _C_ with a circular locking face made to conform to the arc _g_, would permit movement in the direction of the double-headed arrow _y_ with only mechanical effort enough to overcome friction. But it is evident on inspection that a locking face on the line _A b_ would cause a retrograde motion of the escape wheel, and consequent resistance, if said pallet was moved in either direction indicated by the double-headed arrow _y_. Precisely the same conditions obtain at the point _u_, which holds the same relations to the exit pallet as the point _o_ does to the entrance pallet _C_.

ANGULAR MOTION OF ESCAPE WHEEL DETERMINED.

The arc (three and a half degrees) of the circle _a_ embraced between the radial lines _A b_ and _A e_ determines the angular motion of the escape wheel utilized by the escape-wheel tooth. To establish and define the extent of angular motion of the escape wheel utilized by the pallet, we lay off seven degrees on the arc _a_ from the point _o_ and establish the point _n_, and through the point _n_, from _B_ as a center, we sweep the short arc _n'_. Now somewhere on this arc _n'_ will be located the inner angle of the entrance pallet. With a carefully-made drawing, having the escape wheel 10" in diameter, it will be seen that the arc _a_ separates considerably from the line, _B f'_ where it crosses the arc _n'_.

It will be remembered that when drawing the ratchet-tooth lever escapement a measurement of eight and a half degrees was made on the arc _n'_ down from its intersection with the pitch circle, and thus the inner angle of the pallet was located. In the present instance the addendum line _w_ becomes the controlling arc, and it will be further noticed on the large drawing that the line _B h_ at its intersection with the arc _n'_ approaches nearer to the arc _w_ than does the line _B f'_ to the pitch circle _a_; consequently, the inner angle of the pallet should not in this instance be carried down on the arc _n'_ so far to correct the error as in the ratchet tooth.

Reason tells us that if we measure ten degrees down on the arc _n'_ from its intersection with the addendum circle _w_ we must define the position of the inner angle of the entrance pallet. We name the point so established the point _r_. The outer angle of this pallet is located at the intersection of the radial line _A b_ with the line _B i_; said intersection we name the point _v_. Draw a line from the point _v_ to the point _r_, and we define the impulse face of the entrance pallet; and the angular motion obtained from it as relates to the pallet staff embraces six degrees.

Measured on the arc _l_, the entire ten degrees of angular motion is as follows: Two and a half degrees from the impulse face of the tooth, and indicated between the lines _B h_ and _B f_; one and a half degrees lock between the lines _B f'_ and _B i_; six degrees impulse from pallet face, entrance between the lines _B i_ and _B j_.

A DEPARTURE FROM FORMER PRACTICES.

Grossmann and Britten, in all their delineations of the club-tooth escapement, show the exit pallet as disengaged. To vary from this beaten track we will draw our exit pallet as locked. There are other reasons which prompt us to do this, one of which is, pupils are apt to fall into a rut and only learn to do things a certain way, and that way just as they are instructed.

To illustrate, the writer has met several students of the lever escapement who could make drawings of either club or ratchet-tooth escapement with the lock on the entrance pallet; but when required to draw a pallet as illustrated at Fig. 23, could not do it correctly. Occasionally one could do it, but the instances were rare. A still greater poser was to request them to delineate a pallet and tooth when the action of escaping was one-half or one-third performed; and it is easy to understand that only by such studies the master workman can thoroughly comprehend the complications involved in the club-tooth lever escapement.

AN APT ILLUSTRATION.

As an illustration: Two draughtsmen, employed by two competing watch factories, each designs a club-tooth escapement. We will further suppose the trains and mainspring power used by each concern to be precisely alike. But in practice the escapement of the watches made by one factory would "set," that is, if you stopped the balance dead still, with the pin in the fork, the watch would not start of itself; while the escapement designed by the other draughtsman would not "set"--stop the balance dead as often as you choose, the watch would start of itself. Yet even to experienced workmen the escape wheels and pallets _looked_ exactly alike. Of course, there was a difference, and still none of the text-books make mention of it.

For the present we will go on with delineating our exit pallet. The preliminaries are the same as with former drawings, the instructions for which we need not repeat. Previous to drawing the exit pallet, let us reason on the matter. The point _r_ in Fig. 23 is located at the intersection of pitch circle _a_ and the radial line _A c_; and this will also be the point at which the tooth _C_ will engage the locking face of the exit pallet.

This point likewise represents the advance angle of the engaging tooth. Now if we measure on the arc _k_ (which represents the locking faces of both pallets) downward one and a half degrees, we establish the lock of the pallet _E_. To get this one and a half degrees defined on the arc _k_, we set the dividers at 5", and from _B_ as a center sweep the short arc _i_, and from the intersection of the arc _i_ with the line _B e_ we lay off on said arc _i_ one and a half degrees, and through the point so established draw the line _B f_.

Now the space on the arc _k_ between the lines _B e_ and _B f_ defines the angular extent of the locking face. With the dividers set at 5" and one leg resting at the point _r_, we sweep the short arc _t_, and from the intersection of said arc with the line _A c_ we draw the line _n p_; but in doing so we extend it (the line) so that it intersects the line _B f_, and at said intersection is located the inner angle of the exit pallet. This intersection we will name the point _n_.

From the intersection of the line _B e_ with the arc _i_ we lay off two and a half degrees on said arc, and through the point so established we draw the line _B g_. The intersection of this line with the arc _k_ we name the point _z_. With one leg of our dividers set at _A_ we sweep the arc _l_ so it passes through the point _z_. This last arc defines the addendum of the escape-wheel teeth. From the point _r_ on the arc _a_ we lay off three and a half degrees, and through the point so established draw the line _A j_.

LOCATING THE OUTER ANGLE OF THE IMPULSE PLANES.

The intersection of this line with the addendum arc _l_ locates the outer angle of the impulse planes of the teeth, and we name it the point _x_. From the point _r_ we lay off on the arc _a_ seven degrees and establish the point _v_, which defines the extent of the angular motion of the escape wheel utilized by pallet. Through the point _v_, from _B_ as a center, we sweep the short arc _m_. It will be evident on a moment's reflection that this arc _m_ must represent the path of movement of the outer angle of the exit pallet, and if we measure down ten degrees from the intersection of the arc _l_ with the arc _m_, the point so established (which we name the point _s_) must be the exact position of the outer angle of the pallet during locking. We have a measure of ten degrees on the arc _m_, between the lines _B g_ and _B h_, and by taking this space in the dividers and setting one leg at the intersection of the arc _l_ with the arc _m_, and measuring down on _m_, we establish the point _s_. Drawing a line from point _n_ to point _s_ we define the impulse face of the pallet.

MAKING AN ESCAPEMENT MODEL.

It is next proposed we apply the theories we have been considering and make an enlarged model of an escapement, as shown at Figs. 24 and 25. This model is supposed to have an escape wheel one-fifth the size of the 10" one we have been drawing. In the accompanying cuts are shown only the main plate and bridges in full lines, while the positions of the escape wheel and balance are indicated by the dotted circles _I B_. The cuts are to no precise scale, but were reduced from a full-size drawing for convenience in printing. We shall give exact dimensions, however, so there will be no difficulty in carrying out our instructions in construction.

Perhaps it would be as well to give a general description of the model before taking up the details. A reduced side view of the complete model is given at Fig. 26. In this cut the escapement model shown at Figs. 24 and 25 is sketched in a rough way at _R_, while _N_ shows a glass cover, and _M_ a wooden base of polished oak or walnut. This base is recessed on the lower side to receive an eight-day spring clock movement, which supplies the motive power for the model. This base is recessed on top to receive the main plate _A_, Fig. 24, and also to hold the glass shade _N_ in position. The base _M_ is 2½" high and 8" diameter. The glass cover _N_ can have either a high and spherical top, as shown, or, as most people prefer, a flattened oval.

The main plate _A_ is of hard spring brass, 1/10" thick and 6" in diameter; in fact, a simple disk of the size named, with slightly rounded edges. The top plate, shown at _C_, Figs. 24 and 25, is 1/8" thick and shaped as shown. This plate (_C_) is supported on two pillars ½" in diameter and 1¼" high. Fig. 25 is a side view of Fig. 24 seen in the direction of the arrow _p_. The cock _D_ is also of 1/8" spring brass shaped as shown, and attached by the screw _f_ and steady pins _s s_ to the top plate _C_. The bridge _F G_ carries the top pivots of escape wheel and pallet staff, and is shaped as shown at the full outline. This bridge is supported on two pillars ½" high and ½" in diameter, one of which is shown at _E_, Fig. 25, and both at the dotted circles _E E'_, Fig. 24.

To lay out the lower plate we draw the line _a a_ so it passes through the center of _A_ at _m_. At 1.3" from one edge of _A_ we establish on the line _a_ the point _d_, which locates the center of the escape wheel. On the same line _a_ at 1.15" from _d_ we establish the point _b_, which represents the center of the pallet staff. At the distance of 1.16" from _b_ we establish the point _c_, which represents the center of the balance staff. To locate the pillars _H_, which support the top plate _C_, we set the dividers at 2.58", and from the center _m_ sweep the arc _n_.

From the intersection of this arc with the line _a_ (at _r_) we lay off on said arc _n_ 2.1" and establish the points _g g'_, which locate the center of the pillars _H H_. With the dividers set so one leg rests at the center _m_ and the other leg at the point _d_, we sweep the arc _t_. With the dividers set at 1.33" we establish on the arc _t_, from the point _d_, the points _e e'_, which locate the position of the pillars _E E'_. The outside diameter of the balance _B_ is 3-5/8" with the rim 3/16" wide and 5/16" deep, with screws in the rim in imitation of the ordinary compensation balance.

Speaking of a balance of this kind suggests to the writer the trouble he experienced in procuring material for a model of this kind--for the balance, a pattern had to be made, then a casting made, then a machinist turned the casting up, as it was too large for an American lathe. A hairspring had to be specially made, inasmuch as a mainspring was too short, the coils too open and, more particularly, did not look well. Pallet jewels had to be made, and lapidists have usually poor ideas of close measurements. Present-day conditions, however, will, no doubt, enable the workman to follow our instructions much more readily.

MAKING THE BRIDGES.

In case the reader makes the bridges _C_ and _F_, as shown in Fig. 27, he should locate small circles on them to indicate the position of the screws for securing these bridges to the pillars which support them, and also other small circles to indicate the position of the pivot holes _d b_ for the escape wheel and pallet staff. In practice it will be well to draw the line _a a_ through the center of the main plate _A_, as previously directed, and also establish the point _d_ as therein directed.

The pivot hole _d'_ for the escape wheel, and also the holes at _e e_ and _b_, are now drilled in the bridge _F_. These holes should be about 1/16" in diameter. The same sized hole is also drilled in the main plate _A_ at _d_. We now place a nicely-fitting steel pin in the hole _d'_ in the bridge _F_ and let it extend into the hole _d_ in the main plate. We clamp the bridge _F_ to _A_ so the hole _b_ comes central on the line _a_, and using the holes _e e_ in _F_ as guides, drill or mark the corresponding holes _e' e'_ and _b_ in the main plate for the pillars _E E'_ and the pallet staff.

This plan will insure the escape wheel and pallet staff being perfectly upright. The same course pursued with the plate _C_ will insure the balance being upright. The pillars which support the bridges are shaped as shown at Fig. 28, which shows a side view of one of the pillars which support the top plate or bridge _C_. The ends are turned to ¼" in diameter and extend half through the plate, where they are held by screws, the same as in American movements.

The pillars (like _H_) can be riveted in the lower plate _A_, but we think most workmen will find it more satisfactory to employ screws, as shown at Fig. 29. The heads of such screws should be about 3/8" in diameter and nicely rounded, polished and blued. We would not advise jeweling the pivot holes, because there is but slight friction, except to the foot of the balance pivot, which should be jeweled with a plano-convex garnet.

IMITATION RUBIES FOR CAPPING THE TOP PIVOTS.

The top pivots to the escape wheel should be capped with imitation rubies for appearance sake only, letting the cap settings be red gold, or brass red gilded. If real twelve-karat gold is employed the cost will not be much, as the settings are only about 3/8" across and can be turned very thin, so they will really contain but very little gold. The reason why we recommend imitation ruby cap jewels for the upper holes, is that such jewels are much more brilliant than any real stone we can get for a moderate cost. Besides, there is no wear on them.

The pallet jewels are also best made of glass, as garnet or any red stone will look almost black in such large pieces. Red carnelian has a sort of brick-red color, which has a cheap appearance. There is a new phosphorus glass used by optical instrument makers which is intensely hard, and if colored ruby-red makes a beautiful pallet jewel, which will afford as much service as if real stones were used; they are no cheaper than carnelian pallets, but much richer looking. The prettiest cap for the balance is one of those foilback stones in imitation of a rose-cut diamond.

In turning the staffs it is the best plan to use double centers, but a piece of Stubs steel wire that will go into a No. 40 wire chuck, will answer; in case such wire is used, a brass collet must be provided. This will be understood by inspecting Fig. 30, where _L_ represents the Stubs wire and _B N_ the brass collet, with the balance seat shown at _k_. The escape-wheel arbor and pallet staff can be made in the same way. The lower end of the escape wheel pivot is made about ¼" long, so that a short piece of brass wire can be screwed upon it, as shown in Fig. 31, where _h_ represents the pivot, _A_ the lower plate, and the dotted line at _p_ the brass piece screwed on the end of the pivot. This piece _p_ is simply a short bit of brass wire with a female screw tapped into the end, which screws on to the pivot. An arm is attached to _p_, as shown at _T_. The idea is, the pieces _T p_ act like a lathe dog to convey the power from one of the pivots of an old eight-day spring clock movement, which is secured by screws to the lower side of the main plate _A_. The plan is illustrated at Fig. 32, where _l_ represents pivot of the eight-day clock employed to run the model. Counting the escape-wheel pivot of the clock as one, we take the third pivot from this in the clock train, placing the movement so this point comes opposite the escape-wheel pivot of the model, and screw the clock movement fast to the lower side of the plate _A_. The parts _T_, Fig. 33, are alike on both pivots.

PROFITABLE FOR EXPLAINING TO A CUSTOMER.

To fully appreciate such a large escapement model as we have been describing, a person must see it with its great balance, nearly 4" across, flashing and sparkling in the show window in the evening, and the brilliant imitation ruby pallets dipping in and out of the escape wheel. A model of this kind is far more attractive than if the entire train were shown, the mystery of "What makes it go?" being one of the attractions. Such a model is, further, of great value in explaining to a customer what you mean when you say the escapement of his watch is out of order. Any practical workman can easily make an even $100 extra in a year by making use of such a model.

For explaining to customers an extra balance cock can be used to show how the jewels (hole and cap) are arranged. Where the parts are as large as they are in the model, the customer can see and understand for himself what is necessary to be done.

It is not to be understood that our advice to purchase the jewels for an extra balance cock conflicts with our recommending the reader not to jewel the holes of his model. The extra cock is to be shown, not for use, and is employed solely for explaining to a customer what is required when a pivot or jewel is found to be broken.

HOW LARGE SCREWS ARE MADE.

The screws which hold the plates in place should have heads about 3/8" in diameter, to be in proportion to the scale on which the balance and escape wheel are gotten up. There is much in the manner in which the screw heads are finished as regards the elegance of such a model. A perfectly flat head, no matter how highly polished, does not look well, neither does a flattened conehead, like Fig. 35. The best head for this purpose is a cupped head with chamfered edges, as shown at Fig. 34 in vertical section. The center _b_ is ground and polished into a perfect concave by means of a metal ball. The face, between the lines _a a_, is polished dead flat, and the chamfered edge _a c_ finished a trifle convex. The flat surface at _a_ is bright, but the concave _b_ and chamfer at _c_ are beautifully blued. For a gilt-edged, double extra head, the chamfer at _c_ can be "snailed," that is, ground with a suitable lap before bluing, like the stem-wind wheels on some watches.

FANCY SCREWHEADS.

There are two easy methods of removing the blue from the flat part of the screwhead at _a_. (1) Make a special holder for the screw in the end of a cement brass, as shown at _E_, Fig. 36, and while it is slowly revolving in the lathe touch the flat surface _a_ with a sharpened pegwood wet with muriatic acid, which dissolves the blue coating of oxide of iron. (2) The surface of the screwhead is coated with a very thin coating of shellac dissolved in alcohol and thoroughly dried, or a thin coating of collodion, which is also dried. The screw is placed in the ordinary polishing triangle and the flat face at _a_ polished on a tin lap with diamantine and oil. In polishing such surfaces the thinnest possible coating of diamantine and oil is smeared on the lap--in fact, only enough to dim the surface of the tin. It is, of course, understood that it is necessary to move only next to nothing of the material to restore the polish of the steel. The polishing of the other steel parts is done precisely like any other steel work.

The regulator is of the Howard pattern. The hairspring stud is set in the cock like the Elgin three-quarter-plate movement. The richest finish for such a model is frosted plates and bridges. The frosting should not be a fine mat, like a watch movement, but coarse-grained--in fact, the grain of the frosting should be proportionate to the size of the movement. The edges of the bridges and balance cock can be left smooth. The best process for frosting is by acid. Details for doing the work will now be given.

To do this frosting by acid nicely, make a sieve by tacking and gluing four pieces of thin wood together, to make a rectangular box without a bottom. Four pieces of cigar-box wood, 8" long by 1½" wide, answer first rate. We show at _A A A A_, Fig. 37, such a box as if seen from above; with a side view, as if seen in the direction of the arrow _a_, at Fig. 38. A piece of India muslin is glued across the bottom, as shown at the dotted lines _b b_. By turning up the edges on the outside of the box, the muslin bottom can be drawn as tight as a drum head.

HOW TO DO ACID FROSTING.

To do acid frosting, we procure two ounces of gum mastic and place in the square sieve, shown at Fig. 37. Usually more than half the weight of gum mastic is in fine dust, and if not, that is, if the gum is in the shape of small round pellets called "mastic tears," crush these into dust and place the dust in _A_. Let us next suppose we wish to frost the cock on the balance, shown at Fig. 39. Before we commence to frost, the cock should be perfectly finished, with all the holes made, the regulator cap in position, the screw hole made for the Howard regulator and the index arc engraved with the letters S and F.

It is not necessary the brass should be polished, but every file mark and scratch should be stoned out with a Scotch stone; in fact, be in the condition known as "in the gray." It is not necessary to frost any portion of the cock _C_, except the upper surface. To protect the portion of the cock not to be frosted, like the edges and the back, we "stop out" by painting over with shellac dissolved in alcohol, to which a little lampblack is added. It is not necessary the coating of shellac should be very thick, but it is important it should be well dried.

HOW TO PREPARE THE SURFACE.

For illustration, let us suppose the back and edges of the cock at Fig. 39 are coated with shellac and it is laid flat on a piece of paper about a foot square to catch the excess of mastic. Holes should be made in this paper and also in the board on which the paper rests to receive the steady pins of the cock. We hold the sieve containing the mastic over the cock and, gently tapping the box _A_ with a piece of wood like a medium-sized file handle, shake down a little snowstorm of mastic dust over the face of the cock _C_.

Exactly how much mastic dust is required to produce a nice frosting is only to be determined by practice. The way to obtain the knack is to frost a few scraps to "get your hand in." Nitric acid of full strength is used, dipping the piece into a shallow dish for a few seconds. A good-sized soup plate would answer very nicely for frosting the bottom plate, which, it will be remembered, is 6" in diameter.

HOW TO ETCH THE SURFACE.

After the mastic is sifted on, the cock should be heated up to about 250° F., to cause the particles of mastic to adhere to the surface. The philosophy of the process is, the nitric acid eats or dissolves the brass, leaving a little brass island the size of the particle of mastic which was attached to the surface. After heating to attach the particles of mastic, the dipping in nitric acid is done as just described. Common commercial nitric acid is used, it not being necessary to employ chemically pure acid. For that matter, for such purposes the commercial acid is the best.

After the acid has acted for fifteen or twenty seconds the brass is rinsed in pure water to remove the acid, and dried by patting with an old soft towel, and further dried by waving through the air. A little turpentine on a rag will remove the mastic, but turpentine will not touch the shellac coating. The surface of the brass will be found irregularly acted upon, producing a sort of mottled look. To obtain a nice frosting the process of applying the mastic and etching must be repeated three or four times, when a beautiful coarse-grain mat or frosting will be produced.

The shellac protection will not need much patching up during the three or four bitings of acid, as the turpentine used to wash off the mastic does not much affect the shellac coating. All the screw holes like _s s_ and _d_, also the steady pins on the back, are protected by varnishing with shellac. The edges of the cocks and bridges should be polished by rubbing lengthwise with willow charcoal or a bit of chamois skin saturated with oil and a little hard rouge scattered upon it. The frosting needs thorough scratch-brushing.

At Fig. 40 we show the balance cock of our model with modified form of Howard regulator. The regulator bar _A_ and spring _B_ should be ground smooth on one side and deeply outlined to perfect form. The regulator cap _C_ is cut out to the correct size. These parts are of decarbonized cast steel, annealed until almost as soft as sheet brass. It is not so much work to finish these parts as one might imagine. Let us take the regulator bar for an example and carry it through the process of making. The strip of soft sheet steel on which the regulator bar is outlined is represented by the dotted outline _b_, Fig. 41.

To cut out sheet steel rapidly we take a piece of smooth clock mainspring about ¾" and 10" long and double it together, softening the bending point with the lamp until the piece of mainspring assumes the form shown at Fig. 42, where _c_ represents the piece of spring and _H H_ the bench-vise jaws. The piece of soft steel is placed between the limbs of _c c'_ of the old mainspring up to the line _a_, Fig. 41, and clamped in the vise jaws. The superfluous steel is cut away with a sharp and rather thin cold chisel.

The chisel is presented as shown at _G_, Fig. 43 (which is an end view of the vise jaws _H H_ and regulator bar), and held to cut obliquely and with a sort of shearing action, as illustrated in Fig. 42, where _A''_ represents the soft steel and _G_ the cold chisel. We might add that Fig. 42 is a view of Fig. 43 seen in the direction of the arrow _f_. It is well to cut in from the edge _b_ on the line _d_, Fig. 41, with a saw, in order to readily break out the surplus steel and not bend the regulator bar. By setting the pieces of steel obliquely in the vise, or so the line _e_ comes even with the vise jaws, we can cut to more nearly conform to the circular loop _A''_ of the regulator _A_.

The smooth steel surface of the bent mainspring _c_ prevents the vise jaws from marking the soft steel of the regulator bar. A person who has not tried this method of cutting out soft steel would not believe with what facility pieces can be shaped. Any workman who has a universal face plate to his lathe can turn out the center of the regulator bar to receive the disk _C_, and also turn out the center of the regulator spring _B_. What we have said about the regulator bar applies also to the regulator spring _B_. This spring is attached to the cock _D_ by means of two small screws at _n_.

The micrometer screw _F_ is tapped through _B''_ as in the ordinary Howard regulator, and the screw should be about No. 6 of a Swiss screw-plate. The wire from which such screw is made should be 1/10" in diameter. The steel cap _C_ is fitted like the finer forms of Swiss watches. The hairspring stud _E_ is of steel, shaped as shown, and comes outlined with the other parts.

TO TEMPER AND POLISH STEEL.

The regulator bar should be hardened by being placed in a folded piece of sheet iron and heated red hot, and thrown into cold water. The regulator bar _A A'_ is about 3" long; and for holding it for hardening, cut a piece of thin sheet iron 2½" by 3¼" and fold it through the middle lengthwise, as indicated by the dotted line _g_, Fig. 44. The sheet iron when folded will appear as shown at Fig. 45. A piece of flat sheet metal of the same thickness as the regulator bar should be placed between the iron leaves _I I_, and the leaves beaten down with a hammer, that the iron may serve as a support for the regulator during heating and hardening. A paste made of castile soap and water applied to the regulator bar in the iron envelope will protect it from oxidizing much during the heating. The portions of the regulator bar marked _h_ are intended to be rounded, while the parts marked _m_ are intended to be dead flat. The rounding is carefully done, first with a file and finished with emery paper. The outer edge of the loop _A''_ is a little rounded, also the inner edge next the cap _C_. This will be understood by inspecting Fig. 46, where we show a magnified vertical section of the regulator on line _l_, Fig. 40. The curvature should embrace that portion of _A''_ between the radial lines _o o'_, and should, on the model, not measure more than 1/40". It will be seen that the curved surface of the regulator is sunk so it meets only the vertical edge of the loop _A''_. For the average workman, polishing the flat parts _m_ is the most difficult to do, and for this reason we will give entire details. It is to be expected that the regulator bar will spring a little in hardening, but if only a little we need pay no attention to it.

HOW FLAT STEEL POLISHING IS DONE.

Polishing a regulator bar for a large model, such as we are building, is only a heavy job of flat steel work, a little larger but no more difficult than to polish a regulator for a sixteen-size watch. We would ask permission here to say that really nice flat steel work is something which only a comparatively few workmen can do, and, still, the process is quite simple and the accessories few and inexpensive. First, ground-glass slab 6" by 6" by ¼"; second, flat zinc piece 3¼" by 3¼" by ¼"; third, a piece of thick sheet brass 3" by 2" by 1/8"; and a bottle of Vienna lime. The glass slab is only a piece of plate glass cut to the size given above. The zinc slab is pure zinc planed dead flat, and the glass ground to a dead surface with another piece of plate glass and some medium fine emery and water, the whole surface being gone over with emery and water until completely depolished. The regulator bar, after careful filing and dressing up on the edges with an oilstone slip or a narrow emery buff, is finished as previously described. We would add to the details already given a few words on polishing the edges.

It is not necessary that the edges of steelwork, like the regulator bar _B_, Fig. 47, should be polished to a flat surface; indeed, they look better to be nicely rounded. Perhaps we can convey the idea better by referring to certain parts: say, spring to the regulator, shown at _D_, Fig. 40, and also the hairspring stud _E_. The edges of these parts look best beveled in a rounded manner.

It is a little difficult to convey in words what is meant by "rounded" manner. To aid in understanding our meaning, we refer to Figs. 48 and 49, which are transverse sections of _D_, Fig. 50, on the line _f_. The edges of _D_, in Fig. 48, are simply rounded. There are no rules for such rounding--only good judgment and an eye for what looks well. The edges of _D_ as shown in Fig. 49 are more on the beveled order. In smoothing and polishing such edges, an ordinary jeweler's steel burnish can be used.

SMOOTHING AND POLISHING.

The idea in smoothing and polishing such edges is to get a fair gloss without much attention to perfect form, inasmuch as it is the flat surface _d_ on top which produces the impression of fine finish. If this is flat and brilliant, the rounded edges, like _g c_ can really have quite an inferior polish and still look well. For producing the flat polish on the upper surface of the regulator bar _B_ and spring _D_, the flat surface _d_, Figs. 48, 49, 51 and 52, we must attach the regulator bar to a plate of heavy brass, as shown at Fig. 47, where _A_ represents the brass plate, and _B_ the regulator bar, arranged for grinding and polishing flat.

For attaching the regulator bar _B_ to the brass plate _A_, a good plan is to cement it fast with lathe wax; but a better plan is to make the plate _A_ of heavy sheet iron, something about 1/8" thick, and secure the two together with three or four little catches of soft solder. It is to be understood the edges of the regulator bar or the regulator spring are polished, and all that remains to be done is to grind and polish the flat face.

Two pieces _a a_ of the same thickness as the regulator bar are placed as shown and attached to _A_ to prevent rocking. After _B_ is securely attached to _A_, the regulator should be coated with shellac dissolved in alcohol and well dried. The object of this shellac coating is to keep the angles formed at the meeting of the face and side clean in the process of grinding with oilstone dust and oil. The face of the regulator is now placed on the ground glass after smearing it with oil and oilstone dust. It requires but a very slight coating to do the work.

The grinding is continued until the required surface is dead flat, after which the work is washed with soap and water and the shellac dissolved away with alcohol. The final polish is obtained on the zinc lap with Vienna lime and alcohol. Where lathe cement is used for securing the regulator to the plate _A_, the alcohol used with the Vienna lime dissolves the cement and smears the steel. Diamantine and oil are the best materials for polishing when the regulator bar is cemented to the plate _A_.

KNOWLEDGE THAT IS MOST ESSENTIAL.

_The knowledge most important for a practical working watchmaker to possess is how to get the watches he has to repair in a shape to give satisfaction to his customers._ No one will dispute the truth of the above italicised statement. It is only when we seek to have limits set, and define what such knowledge should consist of, that disagreement occurs.

One workman who has read Grossmann or Saunier, or both, would insist on all watches being made to a certain standard, and, according to their ideas, all such lever watches as we are now dealing with should have club-tooth escapements with equidistant lockings, ten degrees lever and pallet action, with one and one-half degrees lock and one and one-half degrees drop. Another workman would insist on circular pallets, his judgment being based chiefly on what he had read as stated by some author. Now the facts of the situation are that lever escapements vary as made by different manufacturers, one concern using circular pallets and another using pallets with equidistant lockings.

WHAT A WORKMAN SHOULD KNOW TO REPAIR A WATCH.

One escapement maker will divide the impulse equally between the tooth and pallet; another will give an excess to the tooth. Now while these matters demand our attention in the highest degree in a theoretical sense, still, for such "know hows" as count in a workshop, they are of but trivial importance in practice.

We propose to deal in detail with the theoretical consideration of "thick" and "thin" pallets, and dwell exhaustively on circular pallets and those with equidistant locking faces; but before we do so we wish to impress on our readers the importance of being able to free themselves of the idea that all lever escapements should conform to the rigid rules of any dictum.

EDUCATE THE EYE TO JUDGE OF ANGULAR AS WELL AS LINEAR EXTENT.

For illustration: It would be easy to design a lever escapement that would have locking faces which were based on the idea of employing neither system, but a compromise between the two, and still give a good, sound action. All workmen should learn to estimate accurately the extent of angular motion, so as to be able to judge correctly of escapement actions. It is not only necessary to know that a club-tooth escapement should have one and one-half degrees drop, but the eye should be educated, so to speak, as to be able to judge of angular as well as linear extent.

Most mechanics will estimate the size of any object measured in inches or parts of inches very closely; but as regards angular extent, except in a few instances, we will find mechanics but indifferent judges. To illustrate, let us refer to Fig. 53. Here we have the base line _A A'_ and the perpendicular line _a B_. Now almost any person would be able to see if the angle _A a B_ was equal to _B a A'_; but not five in one hundred practical mechanics would be able to estimate with even tolerable accuracy the measure the angles made to the base by the lines _b c d_; and still watchmakers are required in the daily practice of their craft to work to angular motions and movements almost as important as to results as diameters.

What is the use of our knowing that in theory an escape-wheel tooth should have one and one-half degrees drop, when in reality it has three degrees? It is only by educating the eye from carefully-made drawings; or, what is better, constructing a model on a large scale, that we can learn to judge of proper proportion and relation of parts, especially as we have no convenient tool for measuring the angular motion of the fork or escape wheel. Nor is it important that we should have, if the workman is thoroughly "booked up" in the principles involved.

As we explained early in this treatise, there is no imperative necessity compelling us to have the pallets and fork move through ten degrees any more than nine and one-half degrees, except that experience has proven that ten degrees is about the right thing for good results. In this day, when such a large percentage of lever escapements have exposed pallets, we can very readily manipulate the pallets to match the fork and roller action. For that matter, in many instances, with a faulty lever escapement, the best way to go about putting it to rights is to first set the fork and roller so they act correctly, and then bring the pallets to conform to the angular motion of the fork so adjusted.

FORK AND ROLLER ACTION.